Introduction: During 1996-97 we performed a pilot study to evaluate how well MR can be used to study changes after a chondrocyte transplantation, a recently described procedure that may lead to reconstitution of articular cartilage which has been damaged by an injury or osteoarthritis. Methods/Results: We evaluated several MR sequences aimed at characterizing cartilage and underlying bone marrow signal changes, as well as contour changes of the transplant. These have included fast spin-echo, SSMT, and a spectroscopy sequence developed by Dr. Garry Gold. The first person to undergo the chondrocyte transplant procedure (Carticel; Genzyme, Inc.) at Stanford has been followed with MR exams performed every 3-4 months for a year, and a few other patients have had MR exams as well. We are planning to examine 12 patients over 2 years post-Carticel procedure, with support from Genzyme, and use other cartilage MR sequences under development as well, such as diffusion imaging, to study these patients. Conclusions: We have shown that subarticular bone marrow edema disappeared within a few months after the chondrocyte transplant, and a smooth surface was formed over the focal cartilage defect that was treated.